The present invention may have applications in all optical fields were it is desired to reconstruct or correct aberrated wavefronts. A specific embodiment of the present invention may be particularly adapted to reconstruct accurate fundus images, provide input for laser surgery of the eye, fabricate corrective lenses and provide accurate digital images of structures sensed through imperfect optical systems.
Aberrations of optical signals occur in many systems and applications. For example, recent interest has been focused on identifying aberrations in the optics of the human eye and correcting these aberrations where possible. Identification of the aberration structure in the optical system offers the possibility of imaging surfaces beyond the aberrating structure or correcting the wavefront exiting the aberrating structure by reshaping the structure or the incident wavefront. In a report entitled xe2x80x9cObjective Measurement of Wave Aberrations of the Human Eye With the Use of a Hartmann-Shack Wave-Front Sensorxe2x80x9d, Liang et al., J. Opt. Soc. Am. A., volume 11, number 7, pp. 1-9, July 1994, the authors disclose the use of a Hartmann-Shack wavefront sensor to measure the wave aberrations of the human eye by sensing the wavefront emerging from the eye produced by the retinal reflection of a focused light beam on the fovea. Due to the limitations of the disclosed system, attempts to improve the system have been made and are disclosed in U.S. Pat. No. 6,095,651 to Williams et al.
The basic diagram of a Hartmann-Shack system is shown in FIGS. 1 and 2. FIG. 1 shows a schematic drawing of a beam of light reflected off the retina (incident beam and beam-shaping optics not shown). In general terms, a ray of light is projected into the eye and reflected off the retina. The reflected wavefront is monitored and spot locations are recorded by a CCD camera or other imaging device. Aberrations are quantified by the deviation of these select rays from the ideal location of rays in an aberration-free system (see FIGS. 2a and 2b).
The device presented in U.S. Pat. No. 6,095,651 projects a single (relatively large diameter) laser beam into the eye. The incident beam covers the entire pupil area (6 to 8 mm in diameter). Before entering the eye, the laser source output is collimated to form a single beam with a parallel shape. The single beam enters the eye where the human optics focus the beam on the retina. The beam is reflected from the retina and passes back through the eye. For this reason, the technique is sometimes referred to as a xe2x80x9cdouble passxe2x80x9d methodxe2x80x94light passes through the optics of the eye twice. The emerging beam travels through multiple lenses (imaging optics) until it finally strikes the HS lenslet array (FIG. 1). The HS lenslet array separates the beam into smaller beamlets. which are focused into spots on an imaging device (typically a CCD camera). The location or displacement of the spots is recorded by the CCD camera.
FIG. 2 illustrates an example of how a uniform wavefront is sensed by the CCD camera and how an aberrating medium changes the wavefront sensed by the CCD camera. The wavefront carries a description of how the original (incident) beam was affected by the optics of the eye. The displacement of the spots from the ideal location roughly corresponds to the aberration properties of the wavefront of the emerging laser beam. If the wavefront is not aberrated or distorted at the location of a particular HS lenslet, the corresponding spot will not be displaced. If the wavefront is highly aberrated then the corresponding spot will be displaced more. The difference between the ideal location and displaced location is the general angle or slope of the wavefront at the lenslet location. Unfortunately, aberrations in the individual lenslets may also contribute to the difference between the ideal location and the displaced location. The slope of the wavefront at many different locations allows one to fit the data to a model of the wavefront.
Previous researchers have applied the re-constructed wavefront information to a compensating device like a deformable mirror. The deformable mirror allows control of a second beam of light (e.g. a flash) so that it is corrected for the aberrating properties in the eye. This technique has demonstrated improved imaging of the retina but fails to provide precise data necessary for accurate imaging.
More recently, as described in xe2x80x9cLaser Ray Tracing Versus Hartmann-Shack Sensor for Measuring Optical Aberrations in the Human Eyexe2x80x9d, Moreno-Barriuso et al., J. Opt. Soc. Am. A., Vol. 17, No. 6, pp. 974-985, have described a technique for using small laser beams they called xe2x80x9cpencils of lightxe2x80x9d to measure aberrations in the eye. They termed the technique xe2x80x9cLaser Ray Tracing.xe2x80x9d In the work, they used a scanning mirror to create a single, small diameter, beamlet that could be moved around the eye in sequential fashion. According to the authors, the technique consists of delivering, sequentially, a series of light pencils (nonexpanded laser beams) coming from the same point object but passing through different locations at the exit pupil plane. The trajectory of the light pencils (rays) is controlled by means of a two dimensional XY optical scanner driven by moving magnet actuators and by additional optics (collimator) when needed. Using this system, the authors were only able to process 4-5 rays per second.
Therefore, there remains a need for improved systems and method of compensating for aberrated wavefronts.
In one aspect of the present invention, a system is provided for imaging through an imperfect optical system. Preferably, the system comprises an energy source generating a plurality of electromagnetic beams having a first configuration for simultaneous transmission through the optical system. A sensor is provided for detecting the plurality of electromagnetic beams after passing through the optical system. A processor is provided that is adapted to utilize the sensed information to calculate the approximate aberrations in the optical system.
In a further aspect of the present invention, an apparatus is provided for use in performing surgery on a living eye. The apparatus may comprise an energy source generating a plurality of electromagnetic beams for simultaneous transmission into a living eye. A camera or other suitable sensor may be located adjacent the eye and in the optical path of a substantial number of the plurality of electromagnetic beams reflected from the living eye to produce digital outputs corresponding to the sensed location of the plurality of electromagnetic beams. A processor receives outputs from the camera or sensor and converts the output signals to a digital signal representative of the optics of the living eye. In a preferred aspect of the invention, surgical equipment may utilize the representative digital signal for performing surgery on the living eye. Still further, the representative digital signal may be used to generate a corrective optic device that corrects all or a part of the sensed aberrations.
In yet a further aspect of the present invention, an apparatus is provided for generating high resolution fundus images of the living eye. Preferably, the apparatus comprises an energy source adapted to generate a plurality of electromagnetic beams in at least one configuration for simultaneous transmission into the living eye. A sensor is included to receive a reflected image of a substantial number of said electromagnetic beams from the living eye and generate a corresponding output signal. A processor may use the output signal to determine wave aberrations of the living eye based on the difference between the first configuration transmitted into the living eye and the reflected image. In a more preferred aspect, a camera receives a fundus image of the living eye and a processor corrects the fundus image based on the calculated wave aberrations. The corrected fundus image may be displayed on a monitor. In still a more preferred aspect, a processing element controls the energy source to generate a plurality of different configurations of the electromagnetic beams.
The present invention also contemplates a method for detecting aberrations of the living eye. The method comprises initially generating a plurality of electromagnetic beams in a first configuration and transmitting the first configuration of electromagnetic beams into a living eye. The electromagnetic beams reflect off structures in the eye and may be received and converted to corresponding digital signals. The digital signals may be used for calculating wave aberrations of the eye. In a preferred aspect, an energy source may be controlled to generate a plurality of electromagnetic beam configurations to accurately detect aberrations of the living eye. Still more preferably, a reference sensor can be used to receive the electromagnetic beam configuration prior to transmitting to the eye. This may be used to improve the accuracy and efficiency of mathematical calculations. In a further alternative, the reference sensor may be used in conjunction with the primary sensor to control an illumination source to generate a beam with an aberrated wavefront corresponding to sensed aberrations in the living eye.
Related objects and advantages of the present invention will be apparent from the following description.